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NOTE: For Ruby 1.9 installation instructions, please see:

   http://wiki.github.com/mark-moseley/ruby-debug

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ruby-debug

Overview

ruby-debug is a fast implementation of the standard debugger debug.rb. The faster execution speed is achieved by utilizing a new hook in the Ruby C API.

Requirements

ruby-debug requires Ruby 1.8.4 or higher.

Unless you get the packages as a binary (Microsoft Windows binaries are sometimes available), you’ll need a C compiler and Ruby development headers, and a Make program so the extension in ruby-debug-base can be compiled when it is installed.

To install on Microsoft Windows, unless you run under cygwin or mingw you’ll need Microsoft Visual C++ 6.0 also known as VC6. rubyforge.org/tracker/index.php?func=detail&aid=16774&group_id=1900&atid=7436 suggests why.

Install

ruby-debug is provided as a RubyGem. To install:

gem install ruby-debug

This should also pull in ruby-debug-base as a dependency.

(If you install ruby-debug-base explicitly, you can add in the --test option after “install” to have the regression test run before installing.)

For Emacs support and the Reference Manual, get ruby-debug-extra. This is not a RubyGem, you’ll need a Make program and a POSIX shell. With this installed, run:

sh ./configure
make
make test # optional, but a good idea
sudo make install

Install on MS Windows

Compiling under cygwin or mingw works like it does on Unix.

  • Have Microsoft Visual C++ 6.0 (VC6) installed - exactly that version.

  • Set the appropriate environment variables.

  • run ‘nmake’.

  • Copy ruby_debug.so to ‘win32’.

  • Go to the ruby_debug root.

  • rake win32_gem

  • The file is in named ‘rdebug-debug-base-0.10.0-mswin32.gem’.

Usage

There are two ways of running ruby-debug.

rdebug executable:

$ rdebug <your-script>

When you start your script this way, the debugger will stop at the first line of code in the script file. So you will be able to set up your breakpoints.

ruby-debug API

The second way is to use the ruby-debug API to interrupt your code execution at run time.

require 'ruby-debug' ; Debugger.start
...
def your_method
  ...
  debugger
  ...
end

or

require 'ruby-debug' ; 
Debugger.start do 
  ...
  debugger
end

When Kernel#debugger method is executed, the debugger is activated and you will be able to inspect and step through your code.

Performance

The debug.rb script that comes with the standard Ruby library uses Kernel#set_trace_func API. Implementing the debugger in pure Ruby has a negative impact on the speed of your program execution. This is because the Ruby interpreter creates a Binding object each trace call, even though it is not being used most of the time. ruby-debug moves most of the functionality for Binding access and for breakpoint testing to a native extension. Because this code is in C and because and can be selectively enabled or disabled, the overhead in running your program can be minimized.

License

See LICENSE for license information.